Electronic devices, for example a cellular handset, a personal digital assistant (PDA), a gaming console or other devices, may be used to handle information, interact with gaming elements and/or to access a communications network. A user will want to interact with the electronic device so as to make or receive calls, send or receive data or interact with software applications.
The electronic device may comprise a display, as would normally be the case for a cellular handset for the displaying of textual or graphical information. The electronic device may comprise a speaker for listening or communicating verbally. The electronic device may comprise a camera for taking images. The electronic device will comprise a user interface so that the user may operate the electronic device.
The functionality present in some electronic devices, for example a cellular handset is increasing, a cellular handset may now comprise a camera, a music player, gaming applications or media related applications. The electronic device must now support different functions and a user interface having only a traditional alphanumeric keypad is not best suited to provide a quick and easy interface between the user and the electronic device, Therefore some user interfaces provide additional input keys such as multi-way navigational key or cylindrical roller body keys, as outlined in EP0901262, which are better suited to navigating menu structures or interfacing with gaining applications. Such navigational keys require their movement or depression be sensed so that items displayed on a display may be activated or browsed.
Navigational keys such as the cylindrical roller key, as outlined in EP0901262, include a mechanical motion sensing means, which permits the user to rotate the key, which may result in a corresponding cursor movement on the display. However in portable electronic devices the overall dimensions must be relatively small to permit the user to carry the electronic device, hence other motion sensing apparatus utilising non mechanical motion sensing apparatus have been adopted.
Motion sensing apparatus as outlined in EP1431713 shows a photo-sensor, comprising a light emitting diode (LED) and a photo-detector, which may be a diode or transistor for the purpose of transmitting and receiving optical signals respectively. Photo-detectors are used for the detection of optical signals and for the conversion of an optical signal to an electrical signal.
The optical signal is directed from the LED to the rotary key input device such that it is reflected from the rotary key towards the photo-detector. The rotary key comprises a plurality of sectors on the surface upon which light is incident, each sector having either a reflective or absorptive characteristic such that as the rotary key is rotated differing amounts of light are received at the photo-detector. Typically, associated circuitry, which utilises the electrical signal from the photo-detector, possibly comprising passive elements such as resistors, biasing elements and transistors may then determine when the rotary key is being rotated by measuring the electrical signal from the photo-detector received over a time period or at a defined time interval and contrasting the measurement with a previous measurement or measurements. Ideally, the electrical signal measured by the associated circuitry due to reflected light from at least two different sectors has a sufficient differential or contrast ratio so that the associated circuitry can determine when the different sectors and therefore the rotary key is being rotated with respect to the photo-sensor. As the rotary key is being rotated the response from the photo-detector as a function of time may look like what is commonly referred to as a ‘square wave’ response. In response to this an electronic device may provide cursor movement on a display or menu browsing in dependence of the rotary movement.
However, the input device must be positioned so as to allow user interaction and will normally be positioned so that it allows freedom of movement, hence there will be an aperture between the electronic device mechanics and the input device near the surface of the mechanical construction of the electronic device. The aperture may allow ambient light to pass and interfere with the photo-detector resulting in an erroneous measurement. Furthermore the mechanical construction of the electronic device may be permeable to light or other EM waves. Ambient light or other EM waves may be able to pass through the mechanical construction and also interfere with the photo-detector. If the motion sensing apparatus is affected by ambient light or other EM waves then the photo-detector may have difficulty in determining when the rotary key input device is being rotated as it may have difficulty in distinguishing when light reflected from the rotary key has been reflected from a reflective or absorptive sector. The contrast ratio between the received light reflected from the two different sectors may be degraded, i.e. it becomes less.
An advantage of the present invention is that there is motion sensing apparatus for determining movement whereby the motion sensing apparatus output is proportional to the intensity of the input energy and said motion sensing apparatus may improve the contrast ratio of the detected energy for different incident energy levels to said motion sensing apparatus.